Immunotherapy

Immunotherapy - Principles & Checkpoint Power

• Core Principle: Enhances host immune system to recognize & eliminate cancer cells by overcoming tumor-induced immunosuppression.
• Checkpoint Inhibitors (CPIs): Monoclonal antibodies that block inhibitory immune checkpoint proteins, releasing the "brakes" on T-cells.
  • CTLA-4 Pathway (Cytotoxic T-Lymphocyte-Associated Protein 4):
    • Ipilimumab: Targets CTLA-4 on T-cells, active during T-cell priming in lymph nodes.
  • PD-1/PD-L1 Pathway (Programmed Death-1 / Programmed Death Ligand-1):
    • PD-1 Inhibitors: Nivolumab, Pembrolizumab (target PD-1 on T-cells).
    • PD-L1 Inhibitors: Atezolizumab, Durvalumab, Avelumab (target PD-L1 on tumor/immune cells).
    • Acts primarily within the tumor microenvironment (effector phase).
• Immune-Related Adverse Events (irAEs):
  • Mechanism: Systemic immune activation due to loss of self-tolerance.
  • Common: Dermatitis, colitis, hepatitis, pneumonitis, endocrinopathies (e.g., hypophysitis, thyroiditis).
  • Severity varies by agent & combination; managed with immunosuppression (e.g., corticosteroids).

⭐ Ipilimumab (anti-CTLA-4) often causes more severe immune-related adverse events (irAEs) like hypophysitis and colitis compared to PD-1/PD-L1 inhibitors, though combination therapy significantly increases overall toxicity.

Immunotherapy - Cellular Soldiers & mAb Strikes

• Cellular Therapies: Patient's immune cells engineered/expanded to fight cancer.
  • CAR T-cell Therapy: T-cells with Chimeric Antigen Receptors (CARs).
    • Targets: CD19 (B-cell ALL, lymphoma), BCMA (Multiple Myeloma).
    • AEs: Cytokine Release Syndrome (CRS), ICANS (neurotoxicity).
  • TILs (Tumor-Infiltrating Lymphocytes): Harvested from tumor, expanded, reinfused. Melanoma.
• Monoclonal Antibodies (mAbs):
  • Immune Checkpoint Inhibitors (ICIs): Block inhibitory signals, unleash T-cell anti-tumor activity.
    • Anti-PD-1: Nivolumab, Pembrolizumab. (📌 Nivo & Pembro for PD-1 Proliferation)
    • Anti-PD-L1: Atezolizumab, Durvalumab, Avelumab.
    • Anti-CTLA-4: Ipilimumab. (📌 Ipi for CTLA-4 Inhibition)
    • Uses: Melanoma, NSCLC, RCC, H&N cancers.
    • AEs: Immune-related Adverse Events (irAEs) - colitis, hepatitis, pneumonitis, endocrinopathies.
  • BiTEs (Bispecific T-cell Engagers): e.g., Blinatumomab (CD19xCD3); links T-cell to tumor.
  • Other Targeted mAbs: Rituximab (anti-CD20), Trastuzumab (anti-HER2).

⭐ Cytokine Release Syndrome (CRS) post CAR T-cell therapy is characterized by fever, hypoxia, and hypotension; Grade ≥2 CRS is managed with Tocilizumab (anti-IL-6R antibody).

Immunotherapy - Modulators, Vaccines & irAE Care

• Cytokine Therapy:
  • IL-2 (Aldesleukin): Metastatic RCC, melanoma. High toxicity (capillary leak).
  • IFN-α: CML, melanoma, hairy cell leukemia. Flu-like symptoms.
• BCG (Bacillus Calmette-Guérin):
  • Intravesical for NMIBC (Non-Muscle Invasive Bladder Cancer). Local immune stimulation.
• Therapeutic Vaccines & Oncolytic Viruses:
  • Sipuleucel-T: Autologous APCs (Antigen-Presenting Cells) for mCRPC (metastatic Castration-Resistant Prostate Cancer).
  • T-VEC (Talimogene laherparepvec): Modified HSV-1 for melanoma; intralesional. Lyses cells, releases GM-CSF.
• Immune-Related Adverse Events (irAEs):
  • Common: Dermatitis, colitis, hepatitis, pneumonitis, endocrinopathies.
  • Management (general):
    • Grade 1: Symptomatic; continue therapy, monitor.
    • Grade 2: Hold therapy; corticosteroids (Prednisone 0.5-1 mg/kg/day). Resume if improves.
    • Grade 3/4: Discontinue therapy; high-dose corticosteroids (Prednisone 1-2 mg/kg/day or IV Methylprednisolone).

  ⭐ For steroid-refractory immune-mediated colitis (Grade ≥3) due to checkpoint inhibitors, Infliximab is the treatment of choice, provided there's no contraindication like active hepatitis. Always rule out infectious causes first.

High‑Yield Points - ⚡ Biggest Takeaways

• Immune Checkpoint Inhibitors (ICIs) like PD-1/PD-L1 (Nivolumab, Pembrolizumab) and CTLA-4 (Ipilimumab) inhibitors are pivotal.
• ICIs commonly cause immune-related adverse events (irAEs) such as colitis, dermatitis, and hepatitis.
• CAR T-cell therapy represents a key adoptive cell transfer strategy.
• Cytokine Release Syndrome (CRS) and neurotoxicity are major toxicities of CAR T-cell therapy.
• Monoclonal antibodies like Rituximab (anti-CD20) target specific tumor antigens effectively.
• Sipuleucel-T is an FDA-approved cancer vaccine for prostate cancer.